The Best Simulator To Me Is:
I use both FS2000 and FMS daily.
MS FSXXX is a very flexible program. I have flown hundreds of hours from both the cockpit (VFR and IFR) and tower views. The tower view offers good feel and fairly good approximation of r/c flight including heading right at ya. The graphics and sound are great, and any the choice of add-on aicraft is endless. But, waiting for the program to reload after a crash is a bummer, and everything happens in real time, so a single pattern to landing takes much longer than r/c. Speeding up the sim helps, but your Cub may fly like a Pitts. MS FS also does a great job with realistic takeoff, landing, and ground handling characteristics of high powered (or not) taildraggers. Try downloading my Blanik L-13 add-on from the SOAR website!
FMS is a great tool for r/c aerobatics practice because the reload is instant, the speeds and distances are more like the real r/c flying site, and the ability to use and program a variety of transmitters or transmitter interfaces better translates to control imputs you'd use at the field. Plus it's free! Ground handling characteristics are not very realistic though. I love playing with it, but so far only so much of what I do in sims helps my r/c flying. In FMS I am working on low, rolling inverted passes with jets. At the flying field I'm only just begining to explore rolling manuvers, and keep my trainers at safer altitudes (cept the Zaggi). I really need to pick up an interface so I can use on of my transmitters. I'm sure that will help the process. The Glider/slope soaring functions in FMS are awesome. THe graphics are great. But, I wish it had prgramable wind. I'm certain that some of the features on RealFlight G2 and other high end sims would be helpful, but FMS is one helluva freebie!
Scott